CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 312,000,000	$ 268,000,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	32,000,000	30,000,000
Deferred income taxes	18,000,000	16,000,000
Premium and discount amortization on available-for-sale securities and loss on other investments	(1,000,000)	8,000,000
Provisions for credit losses and legal and regulatory proceedings	16,000,000	1,000,000
Share-based compensation expense	43,000,000	43,000,000
Unrealized gain on company-owned life insurance policies, net of expenses	(83,000,000)	(35,000,000)
Other	22,000,000	9,000,000
Net change in:
Assets segregated pursuant to regulations excluding cash and cash equivalents	(2,749,000,000)	0
Collateralized agreements, net of collateralized financings	(62,000,000)	21,000,000
Loans provided to financial advisors, net of repayments	5,000,000	(12,000,000)
Brokerage client receivables and other accounts receivable, net	254,000,000	188,000,000
Trading instruments, net	22,000,000	4,000,000
Derivative instruments, net	(9,000,000)	52,000,000
Other assets	(530,000,000)	(81,000,000)
Brokerage client payables and other accounts payable	4,953,000,000	465,000,000
Accrued compensation, commissions and benefits	(253,000,000)	(340,000,000)
Purchases and originations of loans held for sale, net of proceeds from sales of securitizations and loans held for sale	(86,000,000)	(91,000,000)
Net cash provided by operating activities	1,904,000,000	546,000,000
Cash flows from investing activities:
Additions to property and equipment	(25,000,000)	(36,000,000)
Increase in bank loans, net	(704,000,000)	(365,000,000)
Proceeds from sales of loans held for investment	16,000,000	25,000,000
Purchases of available-for-sale securities	(1,243,000,000)	(314,000,000)
Available-for-sale securities maturations, repayments and redemptions	544,000,000	206,000,000
Proceeds from sales of available-for-sale securities	519,000,000	0
Business acquisitions, net of cash acquired	(218,000,000)	0
Other investing activities, net	(12,000,000)	(18,000,000)
Net cash used in investing activities	(1,123,000,000)	(502,000,000)
Cash flows from financing activities:
Proceeds from short-term borrowings, net	0	6,000,000
Exercise of stock options and employee stock purchases	18,000,000	25,000,000
Increase in bank deposits	989,000,000	694,000,000
Purchases of treasury stock	(18,000,000)	(19,000,000)
Dividends on common stock	(55,000,000)	(51,000,000)
Net cash provided by financing activities	908,000,000	654,000,000
Currency adjustment:
Effect of exchange rate changes on cash	73,000,000	21,000,000
Net increase in cash and cash equivalents, including those segregated pursuant to regulations	1,762,000,000	719,000,000
Cash and cash equivalents, including those segregated pursuant to regulations at beginning of year	9,634,000,000	5,971,000,000
Cash and cash equivalents, including those segregated pursuant to regulations at end of period	11,396,000,000	6,690,000,000
Cash and cash equivalents	5,377,000,000	4,109,000,000
Cash and cash equivalents segregated pursuant to regulations	6,019,000,000	2,581,000,000
Supplemental disclosures of cash flow information:
Cash paid for interest	35,000,000	39,000,000
Cash paid for income taxes, net	67,000,000	9,000,000
Cash outflows for lease liabilities	27,000,000	23,000,000
Non-cash right-of-use (“ROU”) assets recorded for new and modified leases	50,000,000	12,000,000
FHLB advances
Cash flows from financing activities:
Proceeds from Federal Home Loan Bank advances	0	850,000,000
Repayments of Federal Home Loan Bank advances and other borrowed funds	$ (26,000,000)	$ (851,000,000)